Hybrid construction equipment power control apparatus

ABSTRACT

Maximum charging power of a battery ( 63 ) is set by a battery-charging power setting unit ( 75 ), while maximum discharging power of the battery ( 63 ) is set by a battery-discharging power setting unit ( 76 ). Lower and upper limit of generator output power is set by a generator output power setting unit ( 77 ). A generator/battery power distribution determining unit ( 81 ) distributes power between the battery ( 63 ) and the generator ( 62 ) using the set values above.

TECHNICAL FIELD

[0001] The present invention relates to a power controller forcontrolling output power of generator and charging/discharging power ofelectrical energy storage unit, both installed in hybrid constructionmachine.

BACKGROUND ART

[0002] Engine for self-traveling has been installed in constructionmachine such as hydraulic excavators and the like, the engine operatingas a power source to drive hydraulic pump and supply each hydraulicactuator such as rotating actuators, boom cylinders, arm cylinders etc.with hydraulic oil discharged from the hydraulic pump, to drive eachportion. However, known construction machine using engine as powersource suffer from problems in that they burn too much gas due to largeload fluctuation and inordinate burden to the engine, and that theygenerate noise and/or exhaust gas emissions. Accordingly, hybridconstruction machine containing motors driven by combination ofgenerator and electrical energy storage unit (battery) have beendeveloped to overcome the foregoing deficiencies. As examples of thehybrid construction machine, there have been provided a series systemone disclosed in Japanese Patent Laid-Open Publication No. 2000-283107and a parallel system one disclosed in Japanese Patent Laid-OpenPublication No. Hei 10-42587/Laid-Open Publication No.2000-226183 etc.

[0003] Generally in either system of the hybrid construction machineabove, voltage between battery terminals has been measured and thebattery state-of-charge SOC has been calculated based on the measurementresults. Then, generator has been operated when the state-of-charge SOCbecome a specified value or less, while the generator has been halted,or the output of the generator has been reduced when the state-of-chargeSOC become the specified value or more. With such control, thestate-of-charge SOC of the battery has been kept within a specifiedrange.

[0004] However, the foregoing state-of-charge SOC based control havesuffered from the problem in that halting generator, or reducing theoutput of the generator caused drop of efficiencies of engine andgenerator in case of small load and high state-of-charge SOC. Inaddition, the foregoing state-of-charge SOC based control in the samecase above have also suffer from the problem in that there might be asituation that electric actuators might not be supplied with electricpower required for its operation because of time-lag to restart engineonce halted, and it was required to increase battery capacity toovercome the problem. Therefore, it was difficult to achieve theconditions simultaneously of supplying appropriate electric powerrequired for electric actuator, controlling battery state-of-charge,operating engine and generator highly efficiently. For example, if itwas prioritized to operate engine and generator highly efficiently,battery capacity was resulted in increase in case of small load ofelectric actuator, and therefore it was difficult to control batterystate-of-charge SOC within a specified range. In contrast, if it wasprioritized to control battery state-of-charge SOC within a specifiedrange, output power fluctuation due to load fluctuation of engine andgenerator was resulted in increase, and therefore efficiencies of engineand generator drop.

[0005] In addition, charging/discharging over battery capacity in caseof low battery temperature would have been likely to cause theperformance deterioration of the battery because of batterycharacteristics that charging/discharging capacity depend on itstemperature. Further, controlling only based on battery state-of-chargeSOC would have been likely to cause the increase of loss because lossesof battery and generator vary with output powers of generator andbattery respectively while internal loss of battery varies with inputpower of the battery.

DISCLOSURE OF THE INVENTION

[0006] Accordingly, an object of the present invention is to provide apower controller for hybrid construction machine which makes it possibleto prevent performance deterioration of its battery due tocharging/discharging over the battery capacity as well as to improvefuel consumption of its engine. It is another object of the presentinvention to provide a power controller for hybrid construction machine,which makes it possible to improve fuel consumption of its engine.

[0007] A power controller for hybrid construction machine of the presentinvention, including an engine, a generator which is driven by theengine, an electrical energy storage unit to store electric powergenerated by the generator, and one or more electric actuators driven bythe generator and the electrical energy storage unit, is characterizedby comprising a load power detecting means to detect required power forthe one or more electric actuators; a charging power setting means toset maximum value of charging power of the electrical energy storageunit; a discharging power setting means to set maximum value ofdischarging power of the electrical energy storage unit; a generatoroutput power setting means to set upper limit and lower limit value ofthe output power of the generator; a power distribution determiningmeans to determine power distribution between the generator and theelectrical energy storage unit based on the set value by the chargingpower setting means, the set value by the discharging power settingmeans, the set value by the generator output power setting means, andthe required power as the detection result by the load power detectingmeans; a generator power controlling means to control output power ofthe generator based on the determined power distribution as thedetermination result by the power distribution determining means; and apower controlling means for electrical energy storage unit to controlcharging/discharging power of the electrical energy storage unit basedon the determination result by the power distribution determining means.

[0008] The power controller for hybrid construction machine above makesit possible to improve fuel consumption of the engine as well as toprevent performance deterioration of the electrical energy storage unitif upper limit and lower limit value of the generator are set within arange to operate the engine and the generator highly efficiently, andmaximum value of charging/discharging power for the electrical energystorage unit is set so that the electrical energy storage unit is notcharged/discharged over its capacity.

[0009] The power controller for hybrid construction machine mentionedabove is characterized by further comprising a state-of-charge detectingmeans to detect state-of-charge of the electrical energy storage unit,wherein the generator output power setting means sets upper limit andlower limit value of the output power of the generator based on thedetected state-of-charge as the detection result by the state-of-chargedetecting means. This power controller makes it possible to controloutput power of the generator and charging/discharging power of theelectrical energy storage unit according to the state-of-charge of theelectrical energy storage unit, wherein the upper limit and the lowerlimit value of output power of the generator are set according to thestate-of-charge of the electrical energy storage unit.

[0010] The power controller for hybrid construction machine mentionedabove is characterized by further comprising a state-of-charge detectingmeans to detect state-of-charge of the electrical energy storage unit,wherein the charging power setting means sets maximum value of thecharging power of the electrical energy storage unit based on thedetection result by the state-of-charge detecting means, and thedischarging power setting means sets maximum value of the dischargingpower of the electrical energy storage unit based on the detectionresult by the state-of-charge detecting means. This power controllermakes it possible to prevent performance deterioration of the electricalenergy storage unit due to charging/discharging over its capacity as aresult of prevention of charging/discharging over the capacityregardless of the state-of-charge of the electrical energy storage unit,wherein maximum values of the charging power and the discharging powerof the electrical energy storage unit are set according to itsstate-of-charge even though the charging/discharging capacity of theelectrical energy storage unit varies depending on its state-of-charge.

[0011] The power controller for hybrid construction machine mentionedabove is characterized by further comprising a temperature detectingmeans to detect temperature of the electrical energy storage unit,wherein the charging power setting means sets maximum value of thecharging power of the electrical energy storage unit based on thedetected temperature as the detection result by the temperaturedetecting means, and the discharging power setting means sets maximumvalue of the discharging power of the electrical energy storage unitbased on the detection result by the temperature detecting means. Thispower controller makes it possible to prevent performance deteriorationof the electrical energy storage unit due to charging/discharging overits capacity as a result of prevention of charging/discharging over thecapacity regardless of the temperature of the electrical energy storageunit, wherein maximum values of the charging power and the dischargingpower of the electrical energy storage unit are set according to itstemperature even though the charging/discharging capacity of theelectrical energy storage unit varies depending on its temperature.

[0012] Another power controller for hybrid construction machine of thepresent invention, including an engine, a generator which is driven bythe engine, an electrical energy storage unit to store electric powergenerated by the generator, and one or more electric actuators driven bythe generator and the electrical energy storage unit, is characterizedby comprising a load power detecting means to detect required power forthe one or more electric actuators; a power distribution determiningmeans to determine power distribution between the generator and theelectrical energy storage unit to maximize power consumption efficiencyby the engine, utilizing the required power detected by the load powerdetecting means, the loss characteristics of the generator and theengine against an output power of the generator, and the losscharacteristics of the electrical energy storage unit against an inputpower of the electrical energy storage unit; a generator powercontrolling means to control output power of the generator based on thedetermined power distribution as the determination result by the powerdistribution determining means; and a power controlling means forelectrical energy storage unit to control input power of the electricalenergy storage unit based on the determination result by the powerdistribution determining means.

[0013] The power controller for hybrid construction machine mentionedabove makes it possible to improve fuel consumption of the engine causedby reducing total energy loss of the hybrid construction machine,wherein output power of the generator and charging/discharging power ofthe electrical energy storage unit are determined taking intoconsideration the loss characteristics of the generator and the engineagainst the output power of the generator, and the loss characteristicsof the electrical energy storage unit against the input power of theelectrical energy storage unit.

[0014] The power controller for hybrid construction machine mentionedabove is characterized by further comprising a temperature detectingmeans to detect temperature of the electrical energy storage unit; and apower loss characteristics determining means for electrical energystorage unit to determine the loss characteristics of the electricalenergy storage unit against the input power of the electrical energystorage unit based on the detection result by the temperature detectingunit. This power controller makes it possible to improve fuelconsumption of the engine caused by reducing energy loss regardless ofthe temperature of the electrical energy storage unit, wherein the losscharacteristics above is determined according to the temperature of theelectrical energy storage unit.

[0015] The power controller for hybrid construction machine mentionedabove is characterized by further comprising a state-of-charge detectingmeans to detect state-of-charge of the electrical energy storage unit;and a power loss characteristics determining means for electrical energystorage unit to determine the loss characteristics of the electricalenergy storage unit against the input power of the electrical energystorage unit based on the detection result by the state-of-chargedetecting unit. This power controller makes it possible to improve fuelconsumption of the engine caused by reducing energy loss regardless ofthe state-of-charge of the electrical energy storage unit, wherein theloss characteristics above is determined according to thestate-of-charge of the electrical energy storage unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a view showing a frame format of an outlineconfiguration of a hybrid excavator to which a power controllingmechanism of a first embodiment of the present invention is applied.

[0017]FIG. 2 is a block diagram illustrating the power controllingmechanism of the hybrid excavator shown in FIG. 1.

[0018]FIG. 3 is a graph showing charging power characteristics of abattery installed in the hybrid excavator shown in FIG. 1 against itsstate-of-charge SOC.

[0019]FIG. 4 is a graph showing discharging power characteristics of abattery installed in the hybrid excavator shown in FIG. 1 against itsstate-of-charge SOC.

[0020]FIG. 5 is a graph showing upper limit characteristics of agenerator output against the state-of-charge SOC of the batteryinstalled in the hybrid excavator shown in FIG. 1.

[0021]FIG. 6 is a graph showing lower limit characteristics of agenerator output against the state-of-charge SOC of the batteryinstalled in the hybrid excavator shown in FIG. 1.

[0022]FIG. 7 is a flowchart showing a process of the power controllingmethod by the power controlling mechanism shown in FIG. 2.

[0023]FIG. 8 is a flowchart showing a process of the power distributiondetermining processing between the generator and the battery shown inthe flowchart of FIG. 7.

[0024]FIG. 9 is an additional illustration of the power distributiondetermining processing shown in the flowchart of FIG. 8.

[0025]FIG. 10 is a block diagram illustrating another power controllingmechanism of a hybrid excavator according to a second embodiment of thepresent invention.

[0026]FIG. 11 is a graph showing power loss characteristics of thebattery installed in the hybrid excavator shown in FIG. 1 against itsinput power.

[0027]FIG. 12 is a graph showing power loss characteristics of thebattery installed in the hybrid excavator shown in FIG. 1 against itsinput power.

[0028]FIG. 13 is a graph showing power loss characteristics of thegenerator and the battery installed in the hybrid excavator shown inFIG. 1 against the output power of the generator.

[0029]FIG. 14 is a diagram illustrating the power distributiondetermining method by the power controlling mechanism shown in FIG. 10.

[0030]FIG. 15 is a flowchart showing a process of the power controllingmethod by the power controlling mechanism shown in FIG. 10.

BEST MODE FOR CARRYING OUT THE INVENTION

[0031] The present invention will be more fully understood from thefollowing description of preferred embodiments when reference is made tothe accompanying drawings. Though a series system hybrid excavator isdescribed below as an example of a hybrid construction machine, thepresent invention is also applicable for various types of hybridconstruction machine such as parallel system ones etc.

[0032] First Embodiment

[0033] A power controller for hybrid excavator according to a firstembodiment of the present invention will be described below referring tothe accompanying drawings.

[0034] At first, a hybrid excavator to which a power controlleraccording to the first embodiment is applied will be described referringto FIG. 1. It should be noted that FIG. 1 is a view showing a frameformat of an outline configuration of a hybrid excavator.

[0035] In FIG. 1, a hybrid excavator 1 comprises a lower traveling body2, an upper rotating body 3 which is connected rotatably to the centerportion of the upper surface of the lower traveling body 2, and anexcavating attachment 4 which is connected to the front portion of theupper rotating body 3.

[0036] The lower traveling body 2 includes a pair of crawler frames 21arranged at the both ends in parallel, a crawler 22 configured rotatablyaround each crawler frame 21 to contact on the ground surface planarly,a motion reducer 23 and a motor 24 to drive in rotation the crawler 22.The lower traveling body 2 composed as described above drives in forwardand reverse, revolves, rotates the entire hybrid excavator 1, driving inrotation each crawler 22 forward and backward respectively through themotion reducer 23 by the motor 24.

[0037] A pivot 5 as rotating axis is configured orthogonal to the lowertraveling body 2 at the center portion of the upper surface of the lowertraveling body 2. The rotating frame 31 that forms part of the upperrotating body 3 is connected to the upper portion of the pivot 5pivotally. At the upper surface of the rotating frame 31, there isconfigured a cabin 32 for operator's cockpit and a machine housing 34covered with a protective cover 33 as well as one end of a boom 41 and aboom cylinder 42 of the excavating attachment 4 axially up and down.

[0038] In the machine housing 34, there is a rotating motor 35 and arotating motion reducer 36 as well as an integrated actuator Al for boomcomprising a boom motor 37 and a boom pump 38 in an integrated manner.The rotating motor 35 drives in rotating motion the rotating frame 31through the rotating motion reducer 36 with the pivot 5 being a guidedcenter. The integrated actuator A1 is connected to the boom cylinder 42through an unillustrated hydraulic pipe, and drives the end side of theboom 41 up and down.

[0039] At the end of the boom 41, an arm 43 is connected pivotally. Atthe end of the arm 43, a bucket 44 is connected pivotally. In addition,the boom 41 and the arm 43 are connected to each other through an armcylinder 45, while the arm 43 and the bucket 44 are connected to eachother through a bucket cylinder 46. For these cylinders 45 and 46, thereare configured an integrated actuator A2 for arm and an integratedactuator A3 for bucket respectively, wherein the integrated actuator A2comprises an arm motor 47 a and an arm pump 47 b in an integrated mannerwhile the integrated actuator A3 comprises a bucket motor 48 a and abucket pump 48 b in an integrated manner. Each actuator A2, A3 movesforward and backward each cylinder rod of the cylinder 45, 46 byhydraulic pressure to drive the arm 43 and the bucket 44 respectivelyaxially up and down.

[0040] In the machine housing 34, there are installed an engine 61, agenerator 62 to generate AC power according to speed (engine power) ofthe engine 61, as well as a battery 63 (an electrical energy storageunit) etc.

[0041] Next, a power controlling mechanism of the hybrid excavator 1having the configuration above will be described referring to FIG. 2. Itshould be noted that FIG. 2 is a block diagram illustrating the powercontrolling mechanism of the hybrid excavator 1.

[0042] The block diagram shown in FIG. 2 consists of the engine 61, agenerator 62, a battery 63 to store surplus power generated by thegenerator 62 and to supply an electric actuator 64 with powerappropriately, the electric actuator 64, and a power controllingmechanism 7, wherein the power supply from the battery 63 to theelectric actuator 64 and that from the generator 62 to the electricactuator 64 or the battery 63 are made through DC (direct current)voltage lines. The electric actuator 64 represents either the integratedactuator A1 for boom, the integrated actuator A2 for arm or theintegrated actuator A3 for bucket etc., only one out of which beingillustrated in FIG. 2.

[0043] The power controlling mechanism 7 shown in FIG. 2 comprises abattery temperature sensor 71, a battery current sensor 72, a batteryvoltage sensor 73, a battery state-of-charge detecting unit 74, abattery-charging power setting unit 75, a battery-discharging powersetting unit 76, a generator output power setting unit 77, a loadvoltage sensor 78, a load current sensor 79, a load power detecting unit80, a generator/battery power distribution determining unit 81, abattery power controlling unit 82, and a generator power controllingunit 83.

[0044] The battery temperature sensor 71 detects temperature of thebattery 63 and outputs a battery temperature TEMP_(b) as a detectionresult at the battery state-of-charge detecting unit 74, thebattery-charging power setting unit 75, and the battery-dischargingpower setting unit 76. The battery current sensor 72 detects outputcurrent of the battery 63 and outputs an output current I_(b) as adetection result at the battery state-of-charge detecting unit 74. Thebattery voltage sensor 73 also detects voltage between terminals of thebattery 63 and outputs a voltage between terminals V_(b) as a detectionresult at the battery state-of-charge detecting unit 74.

[0045] The battery state-of-charge detecting unit 74 calculates power ofthe battery 63 using the output current I_(b) of the battery 63 inputtedfrom the battery current sensor 72 and the voltage V_(b) betweenterminals of the battery 63 inputted from the battery voltage sensor 73,and then calculates charge quantity J of the battery 63 based on thecalculated power. The battery state-of-charge detecting unit 74 thenoperates the following expression to calculate a ratio of chargequantity J to a maximum charge quantity J_(max) of the battery 63, thatis a state-of-charge SOC (%), and then outputs the SOC as a calculationresult at the battery-charging power setting unit 75, thebattery-discharging power setting unit 76, and the generator outputpower setting unit 77. ${SOC} = {\frac{J}{J_{\max}} \times 100}$

[0046] It should be noted that the SOC of the battery 63 is calculatedcorrecting the voltage V_(b) between terminals by the temperatureTEMP_(b) of the battery 63 detected at the battery temperature sensor 71because the voltage V_(b) detected at the battery voltage sensor 73depends on temperature.

[0047] In addition to above, charge quantity J of the battery 63 may becalculated accumulating voltages V_(b) between terminals or outputcurrents I_(b) of the battery 63, instead of accumulating powers.

[0048] The battery-charging power setting unit 75 determines maximumvalue of the charging power for the battery 63 using the temperatureTEMP_(b) of the battery 63 inputted from the battery temperature sensor71 and the state-of-charge SOC of the battery 63 inputted from thebattery state-of-charge SOC detecting unit 74, and outputs the maximumcharging power P_(bc) as a determination result at the generator/batterypower distribution determining unit 81.

[0049] For details, there are stored predefined values of charging powerof the battery 63 against state-of-charge and temperature of the battery63 in a table (a memory unit) of the battery-charging power setting unit75 as shown in FIG. 3. In addition, values of charging power above areset not to exceed the charging capacity of the battery 63. Based on thetemperature TEMP_(b) and the state-of-charge SOC of the battery 63, thebattery-charging power setting unit 75 takes predefined charging powersetting value corresponding to the temperature TEMP_(b) and thestate-of-charge SOC out of the table.

[0050] The battery-charging power setting unit 75 then determines thetaken setting value as a maximum value of charging power (maximumcharging power P_(bc)) of the battery 63 and outputs P_(bc) at thegenerator/battery power distribution determining unit 81.

[0051] The battery-discharging power setting unit 76 determines maximumvalue of the discharging power for the battery 63 using the temperatureTEMP_(b) of the battery 63 inputted from the battery temperature sensor71 and the state-of-charge SOC of the battery 63 inputted from thebattery state-of-charge SOC detecting unit 74, and outputs the maximumdischarging power P_(bd) as a determination result at thegenerator/battery power distribution determining unit 81.

[0052] For details, there are stored predefined values of dischargingpower of the battery 63 against state-of-charge and temperature of thebattery 63 in a table (a memory unit) of the battery-discharging powersetting unit 76 as shown in FIG. 4. In addition, values of dischargingpower above are set not to exceed the discharging capacity of thebattery 63. Based on the temperature TEMP_(b) and the state-of-chargeSOC of the battery 63, the battery-discharging power setting unit 76takes predefined discharging power setting value corresponding to thetemperature TEMP_(b) and the state-of-charge SOC out of the table. Thebattery-discharging power setting unit 76 then determines the takensetting value as a maximum value of discharging power (maximumdischarging power P_(bd)) of the battery 63 and outputs P_(bd) at thegenerator/battery power distribution determining unit 8·1.

[0053] The generator output power setting unit 77 determines upper limitvalue (upper limit P_(gu) of the generator output) and lower limit value(lower limit P_(gl) of the generator output) of the output power of thegenerator 62 using the state-of-charge SOC of the battery 63 inputtedfrom the battery state-of-charge detecting unit 74, and outputs theupper limit P_(gu) of the generator output and the lower limit P_(gl) ofthe generator output as a determination result at the generator/batterypower distribution determining unit 81.

[0054] For details, there are stored predefined upper limit values ofthe generator output against state-of-charge of the battery 63 andpredefined lower limit values of the generator output againststate-of-charge of the battery 63 in a table (a memory unit) of thegenerator output power setting unit 77 as shown in FIG. 5 and FIG. 6respectively. In addition, upper limit values and lower limit valuesabove are set to make efficiencies of the engine 61 and the generator 62favorable. Based on the state-of-charge SOC of the battery 63, thegenerator output power setting unit 77 takes predefined upper limitvalue of the generator output corresponding to the state-of-charge SOCout of the table, and determines the taken upper limit value as an upperlimit value of the output power of the generator 62 (upper limit P_(gu)of the generator output). Further, Based on the state-of-charge SOC ofthe battery 63, the generator output power setting unit 77 takespredefined lower limit value of the generator output corresponding tothe state-of-charge SOC out of the table, and determines the taken lowerlimit value as a lower limit value of the output power of the generator62 (lower limit P_(gl) of the generator output). Then, the generatoroutput power setting unit 77 outputs determined upper limit P_(gu) ofthe generator output and lower limit P_(gl) of the generator output atthe generator/battery power distribution determining unit 81.

[0055] The load voltage sensor 78 detects voltage at an input unit ofthe electric actuator 64, and outputs load voltage V_(L) as a detectionresult at the load power detecting unit 80. The load current sensor 79detects current at the input unit of the electric actuator 64, andoutputs load current I_(L) as a detection result at the load powerdetecting unit 80.

[0056] The load power detecting unit 80 operates the followingexpression to detect required power P_(L) for the electric actuator 64using the load voltage V_(L) inputted from the load voltage sensor 78and the load current I_(L) inputted from the load current sensor 79, andthen outputs the P_(L) as a detection result at the generator/batterypower distribution determining unit 81.

P _(L) =V _(L) ×I _(L)

[0057] The generator/battery power distribution determining unit 81determines battery power P_(b) and generator power P_(g) based on therequired power P_(L) for the electric actuator 64 inputted from the loadpower detecting unit 80, the maximum charging power P_(bc) inputted fromthe battery-charging power setting unit 75, the maximum dischargingpower P_(bd) inputted from the battery-discharging power setting unit76, the upper limit P_(gu) of the generator output and the lower limitP_(gl) of the generator output inputted from the generator output powersetting unit 77. The generator/battery power distribution determiningunit 81 then outputs a command signal including the battery power P_(b)as a determination result at the battery power controlling unit 82 whileoutputs another command signal including the generator power P_(g) as adetermination result at the generator power controlling unit 83. Theprocessing above will hereinafter be described in detail referring tothe flowchart of FIG. 8.

[0058] The battery power controlling unit 82 controls charge/dischargeof the battery 63 to the battery power P_(b) included in the commandsignal inputted from the generator/battery power distributiondetermining unit 81. The generator power controlling unit 83 alsocontrols generation of the generator 62 to the generator power P_(g)included in the command signal inputted from the generator/battery powerdistribution determining unit 81.

[0059] Further, a power controlling method in the power controllingmechanism 7, which has the foregoing configuration, will be describedreferring to FIG. 7, FIG. 8 and FIG. 9. It should be noted that FIG. 7is a flowchart showing a process of the power controlling method, thatFIG. 8 is a flowchart showing a process of the power distributiondetermining processing between the generator and the battery shown inthe flowchart of FIG. 7. FIG. 9 is an illustration of the powerdistribution determining processing between the generator and thebattery, wherein the solid line represents the generator power P_(g)while the alternate long and short dash line the battery power P_(b).

[0060] In step S101, the battery state-of-charge detecting unit 74calculates state-of-charge SOC of the battery 63 using the outputcurrent I_(b) of the battery 63 inputted from the battery current sensor72 and the voltage V_(b) between terminals of the battery 63 inputtedfrom the battery voltage sensor 73, with the voltage V_(b) betweenterminals being corrected by the temperature TEMP_(b) of the battery 63inputted from the battery temperature sensor 71. The batterystate-of-charge detecting unit 74 then outputs the state-of-charge SOCas a calculation result at the battery-charging power setting unit 75,the battery-discharging power setting unit 76, and the generator outputpower setting unit 77.

[0061] In step S102, the battery-charging power setting unit 75determines maximum value of the charging power of the battery 63 usingthe temperature TEMP_(b) of the battery 63 inputted from the batterytemperature sensor 71 and the state-of-charge SOC of the battery 63inputted from the battery state-of-charge detecting unit 74, and thenoutputs the maximum charging power P_(bc) at the generator/battery powerdistribution determining unit 81.

[0062] In step S103, the battery-discharging power setting unit 76determines maximum value of the discharging power of the battery 63using the temperature TEMP_(b) of the battery 63 inputted from thebattery temperature sensor 71 and the state-of-charge SOC of the battery63 inputted from the battery state-of-charge detecting unit 74, and thenoutputs the maximum discharging power P_(bd) at the generator/batterypower distribution determining unit 81.

[0063] In step S104, the generator output power setting unit 77determines upper limit value (upper limit P_(gu) of the generatoroutput) and lower limit value (lower limit P_(gl) of the generatoroutput) of the output power of the generator 62 using thestate-of-charge SOC of the battery 63 inputted from the batterystate-of-charge detecting unit 74, and outputs the upper limit P_(gu) ofthe generator output and the lower limit P_(gl) of the generator outputas a determination result at the generator/battery power distributiondetermining unit 81.

[0064] In step S105, the load power detecting unit 80 detects requiredpower PL for the electric actuator 64 using the load voltage V_(L)inputted from the load voltage sensor 78 and the load current I_(L)inputted from the load current sensor 79, and then outputs the P_(L) asa detection result at the generator/battery power distributiondetermining unit 81.

[0065] In step S106, the generator/battery power distributiondetermining unit 81 determines generator power P_(g) and battery powerP_(b), and then outputs a command signal including the generator powerP_(g) as a determination result at the generator power controlling unit83 while outputs another command signal including the battery powerP_(b) as a determination result at the battery power controlling unit83. That is, the generator/battery power distribution determining unit81 executes a power distribution determining processing between thegenerator and the battery (refer to FIG. 8).

[0066] In step S107, The battery power controlling unit 82 controlscharge/discharge of the battery 63 to the battery power P_(b) indicatedby the command signal inputted from the generator/battery powerdistribution determining unit 81. In contrast, the generator powercontrolling unit 83 controls generation of the generator 62 to thegenerator power P_(g) indicated by the command signal inputted from thegenerator/battery power distribution determining unit 81.

[0067] Next, the power distribution determining processing between thegenerator and the battery by the power controlling mechanism 7 will bedescribed referring to FIG. 8.

[0068] In step S201, the generator/battery power distributiondetermining unit 81 judges whether or not the required power P_(L) forthe electric actuator 64 is smaller than the negative value of themaximum charging power P_(bc) of the battery 63 (P_(L)<−P_(bc)). In casethe required power P_(L) is smaller than the negative value of themaximum charging power P_(bc) (step S201: YES), the process moves tostep 202 while in case the required power P_(L) is not smaller than thenegative value of the maximum charging power P_(bc) (step S201: NO), theprocess moves to step 203.

[0069] In step S202, the generator/battery power distributiondetermining unit 81 determines the battery power P_(b) of the battery 63and the generator power P_(g) of the generator 62 as “−P_(b)” and “0”respectively, and then finishes the power distribution determiningprocessing. That is, the battery 63 will be charged by the maximumcharging power P_(bc).

[0070] In step S203, the generator/battery power distributiondetermining unit 81 judges whether or not the required power P_(L) forthe electric actuator 64 is within the range of being bigger than thenegative value of the maximum charging power P_(bc) of the battery 63and smaller than the lower limit P_(gl) of the generator power(−P_(bc)≦P_(L)<P_(gl)). In case the required power P_(L) is within therange (step S203: YES), the process moves to step S204 while in case therequired power P_(L) is not within the range (step S203: NO), to stepS207.

[0071] Following the steps above, in step S204, the generator/batterypower distribution determining unit 81 judges whether or not thenegative value of the maximum charging power P_(bc) of the battery 63 isbigger than the value gotten by subtracting the lower limit P_(gl) ofthe generator power from the required power P_(L) for the electricactuator 64 (P_(L)−P_(gl)<−P_(bc)). In case the negative value of themaximum charging power P_(bc) of the battery 63 is bigger than the othervalue (step S204: YES), the process moves to step S205 while in case thenegative value of the maximum charging power P_(bc) of the battery 63 isnot bigger than the other value (step S204: NO), to step S206.

[0072] In step S205, the generator/battery power distributiondetermining unit 81 determines the battery power P_(b) of the battery 63and the generator power P_(g) of the generator 62 as “−P_(bc)” and“P_(L)−(−P_(bc))” respectively (section A2 in FIG. 9), and then finishesthe power distribution determining processing. That is, the battery 63will be charged by the maximum charging power P_(bc), slack of powerrequired to charge the battery by the maximum charging power P_(bc)being taken up with the generator 62. The reason the generator powerP_(g) of the generator 62 falls below the lower limit P_(gl) of thepower of the generator 62 is that the generator 62 should work under thelower limit P_(gl) of the generator power to prevent the battery 63 frombeing charged by power over the maximum charging power P_(bc) of thebattery 63 which may occurs in case the power P_(g) of the generator 62is arranged to the lower limit P_(gl) of the generator power.

[0073] In step S206, the generator/battery power distributiondetermining unit 81 determines the battery power P_(b) of the battery 63and the generator power P_(g) of the generator 62 as “P_(L)−P_(gl)” and“P_(gl)” respectively (section A3 in FIG. 9), and then finishes thepower distribution determining processing. That is, the generator powerP_(g) of the generator 62 will be controlled to the lower limit P_(gl)of the power of the generator 62, surplus of the power generated by thegenerator 62 charging the battery 63.

[0074] In step S207, the generator/battery power distributiondetermining unit 81 judges whether or not the required power P_(L) forthe electric actuator 64 is within the range of bigger than the lowerlimit P_(gl) of the generator power and being the upper limit P_(gu) ofthe generator power or less (P_(gl)≦P_(L)<P_(gu)). In case the requiredpower P_(L) is within the range (step S207: YES), the process moves tostep S208 while in case the required power P_(L) is not within the range(step S207: NO), to step S209.

[0075] In step S208, the generator/battery power distributiondetermining unit 81 determines the battery power P_(b) of the battery 63and the generator power P_(g) of the generator 62 as “0” and “P_(L)”respectively (section A4 in FIG. 9), and then finishes the powerdistribution determining processing. That is, the generator power P_(g)of the generator 62 will be within the range of the lower limit P_(gl)of the generator power or more and being smaller than the upper limitP_(gu) of the generator power, the battery 63 neither charging nordischarging.

[0076] In step S209, the generator/battery power distributiondetermining unit 81 judges whether or not the required power P_(L) forthe electric actuator 64 is within the range of being bigger than theupper limit P_(gu) of the generator power and being the value or moregotten by adding the maximum discharging power P_(bd) of the battery 63to the upper limit P_(gu) of the generator power(P_(gu)≦P_(L)<P_(gu)+P_(bd)). In case the required power P_(L) is withinthe range (step S209: YES), the process moves to step S210 while in casethe required power P_(L) is not within the range (step S209: NO), tostep S211.

[0077] In step S210, the generator/battery power distributiondetermining unit 81 determines the battery power P_(b) of the battery 63and the generator power P_(g) of the generator 62 as “P_(L)−P_(gu)” and“P_(gu)” respectively (section A5 in FIG. 9), and then finishes thepower distribution determining processing. That is, the power P_(g)generated by the generator 62 will be limited to the upper limit P_(gu)of the generator power, and slack of generation power “P_(L)−P_(gu)” bythe generator 62 will be taken up with the battery 63. Moreover, thedischarging power of the battery 63 is the maximum discharging powerP_(bd) or less.

[0078] In step S211, the generator/battery power distributiondetermining unit 81 judges whether or not the required power P_(L) forthe electric actuator 64 is within the range of being the value gottenby adding the maximum discharging power P_(bd) of the battery 63 to theupper limit P_(gu) of the generator power and being smaller than thevalue or more gotten by adding the maximum discharging power P_(bd) ofthe battery 63 to a maximum generator power P_(gmax)(P_(gu)+P_(bd)≦P_(L)<P_(gmax)+P_(bd)). In case the required power P_(L)is within the range (step S211: YES), the process moves to step S212while in case the required power P_(L) is not within the range (stepS211: NO), to step S213. The maximum generator power P_(gmax) is themaximum value of the output power of the generator 62 depending on theperformance of the engine 61 and the generator 62.

[0079] In step S212, the generator/battery power distributiondetermining unit 81 determines the battery power P_(b) of the battery 63and the generator power P_(g) of the generator 62 as “P_(bd)” and“P_(L)−P_(bd)” respectively (section A6 in FIG. 9), and then finishesthe power distribution determining processing. That is, the battery 63is controlled to discharge at the maximum discharging power P_(bd),while the generator 62 is controlled to generate power of“P_(L)−P_(bd)”. The generator 62 works to generate power over the upperlimit P_(gu) of the generator power so as to supply the electricactuator 64 with the required power P_(L) for the electric actuator 64from the generator 62 and the battery 63.

[0080] In step 213, the generator/battery power distribution determiningunit 81 determines the battery power P_(b) of the battery 63 and thegenerator power P_(g) of the generator 62 as “P_(bd)” and “P_(gmax)”respectively (section A7 in FIG. 9), and then finishes the powerdistribution determining processing. That is, the battery 63 iscontrolled to discharge at the maximum discharging power P_(bd), whilethe generator 62 is controlled to generate power of the maximumgenerator power P_(gmax). In this case, all of the required power P_(L)for the electric actuator 64 is not supplied for the electric actuator64.

[0081] In accordance with the power controlling mechanism 7 for thehybrid excavator 1 according to the first embodiment of the presentinvention, the battery 63 is controlled to discharge at the maximumdischarging power P_(bd) or less e.g. not exceeding its dischargingcapacity, and also to charge at the maximum charging power P_(bc) orless e.g. not exceeding its charging capacity, so it is possible toprevent performance deterioration of the battery 63 due tocharging/discharging over the battery capacity.

[0082] In addition, the output power of the generator 62 is controlledto being within the range between the lower limit P_(gl) of thegenerator power and the upper limit P_(gu) of the generator power,efficiencies of the engine 61 and the generator 62 being favorabletherebetween (except for section A2, A6 and A7 in FIG. 9), so the fuelconsumption of the engine 61 is improved.

[0083] Further, it is possible to prevent performance deterioration ofthe battery 63 due to charging/discharging over its capacity as a resultof prevention of charging/discharging over the capacity regardless ofthe state-of-charge of the battery 63, wherein the maximum chargingpower P_(bc) and the maximum discharging power P_(bd) of the battery 63are set according to its state-of-charge even though thecharging/discharging capacity of the battery 63 varies depending on itsstate-of-charge. It is also possible to prevent performancedeterioration of the battery 63 due to charging/discharging over itscapacity as a result of prevention of charging/discharging over thecapacity regardless of the temperature of the battery 63, wherein themaximum charging power P_(bc) and the maximum discharging power P_(bd)of the battery 63 are set according to its temperature even though thecharging/discharging capacity of the battery 63 varies depending on itstemperature.

[0084] Second Embodiment

[0085] A power controller for hybrid excavator according to a secondembodiment of the present invention will be described below referring tothe accompanying drawings. The hybrid excavator 1 in the firstembodiment described using FIG. 1 is available as a hybrid excavator towhich a power controller according to the second embodiment is applied.

[0086] At first, a power controlling mechanism of a hybrid excavatoraccording to the second embodiment will be described referring to FIG.10. It should be noted that FIG. 10 is a block diagram illustrating apower controlling mechanism according to the second embodiment. Elementssubstantially equal to those in the first embodiment are provided withthe same symbols.

[0087] The block diagram shown in FIG. 10 consists of an engine 61, agenerator 62, a battery 63, an electric actuator 64, and a powercontrolling mechanism 9. Power supply from the battery 63 to theelectric actuator 64 and that from the generator 62 to the electricactuator 64 or the battery 63 are made through DC voltage lines. Theelectric actuator 64 represents either an integrated actuator A1 forboom, an integrated actuator A2 for arm or a integrated actuator A3 forbucket etc., only one out of which being illustrated in FIG. 10.

[0088] The power controlling mechanism 9 shown in FIG. 10 comprises abattery temperature sensor 71, a battery current sensor 72, a batteryvoltage sensor 73, a battery state-of-charge detecting unit 74, abattery power-loss characteristics determining unit 91, a generatoroutput power-loss characteristics determining unit 92, a load voltagesensor 78, a load current sensor 79, a load power detecting unit 80, agenerator/battery power distribution determining unit 93, a batterypower controlling unit 82, and a generator power controlling unit 83.Processing details of the battery temperature sensor 71, the batterycurrent sensor 72, the battery voltage sensor 73, the batterystate-of-charge detecting unit 74, the load voltage sensor 78, the loadcurrent sensor 79, the load power detecting unit 80, the battery powercontrolling unit 82, and the generator power controlling unit 83 aresubstantially equal to those described in the first embodiment.

[0089] The battery power-loss characteristics determining unit 91determines loss characteristics of the battery 63 against input power tothe battery 63 using the temperature TEMP_(b) of the battery 63 inputtedfrom the battery temperature sensor 71 and the state-of-charge SOC ofthe battery 63 inputted from the battery state-of-charge detecting unit74, and then outputs coefficients (a, b, c) of quadratic expression inan approximation of the determined characteristics by a quadraticexpression at the generator/battery power distribution determining unit93.

[0090] For details, there are stored coefficients (a, b, c) of quadraticexpression for state-of-charge SOC and temperature TEMP_(b) of thebattery 63 individually, which are obtained by an approximation ofcharacteristics of power loss P2_(bross) of the battery 63 against inputpower P2_(b) to the battery 63 by a quadratic expression representedwith the following expression, in a table (a memory unit) of the batterypower-loss characteristics determining unit 91 as shown in FIG. 11 andFIG. 12, both of which are precedently obtained by executing experimentsetc. In FIG. 11, (a, b, c)=(0.0025, 0.2032, 0).

P2_(bross) =a×P2_(b) ² +b×P2_(b) +c

[0091] Based on the temperature TEMP_(b) and state-of-charge SOC of thebattery 63, the battery power-loss characteristics determining unit 91then takes coefficients (a, b, c) corresponding to the temperatureTEMP_(b) and the state-of-charge SOC out of the table. The batterypower-loss characteristics determining unit 91 outputs the takencoefficients (a, b, c) at the generator/battery power distributiondetermining unit 93.

[0092] There are stored coefficients (α, β, γ) of quadratic expression,which are obtained by an approximation of characteristics of power lossP2_(gross) of the engine and the generator 62 against output powerP2_(g) of the generator 62 by a quadratic expression represented withthe following expression, in a table (a memory unit) of the generatoroutput power-loss characteristics determining unit 92 as shown in FIG.13, which is precedently obtained by executing experiments etc. Then,the battery power-loss characteristics determining unit 91 outputs theprecedently stored coefficients (α, β, γ) at the generator/battery powerdistribution determining unit 93. In FIG. 13, (α, β, γ)=(0.00478,0.0873, 12.303).

P2_(gross) =α×P2_(g) ² +β×P2_(g)+γ

[0093] Based on the coefficients (a, b, c) input from the batterypower-loss characteristics determining unit 91, the coefficients (α, β,γ) inputted from the generator output power-loss characteristicsdetermining unit 92, and the required power P2_(L) for the electricactuator 64 inputted from the load power detecting unit 80, thegenerator/battery power distribution determining unit 93 determinesinput power P2_(b) of the battery 63 and output power P2_(g) of thegenerator 62. Then, the generator/battery power distribution determiningunit 93 outputs a command signal including the input power P2_(b) of thebattery 63 as a determination result at the battery power controllingunit 82 while outputs a command signal including the output power P2_(g)of the generator 62 at the generator power controlling unit 83.

[0094] The power distribution determining method by thegenerator/battery power distribution determining unit 93 willhereinafter be described referring to FIG. 14. It should be noted thatFIG. 14 is a diagram illustrating the power distribution determiningmethod. In FIG. 14, power consumption P2_(gas) represents the powerconsumed by the engine 61 while power loss P2_(gross) the power theengine 61 and the generator 62 lose, output power P2_(g) the power thegenerator 62 outputs, input power P2_(b) the power input to the battery63, power loss P2_(bross) the power the battery 63 lose, and powerconsumption P2_(L) the power consumed by the electric actuator 64.

[0095] Total power loss P2_(tross) in the system shown in FIG. 14 isrepresented with the following expression (1).

P2_(tross) =P2_(gross) +P2_(bross)  (1)

[0096] In addition, an available charging power P2_(bavl), of thebattery 63, which is available for driving the electric actuator 64 outof the input power P2_(b) of the battery 63, is represented with thefollowing expression (2).

P2_(bavl) =P2_(b) −P2_(bross)  (2)

[0097] Further, efficiency η of the entire system shown in FIG. 14 isrepresented with the following expression (3). $\begin{matrix}{\eta = {\frac{{P2}_{L} + {P2}_{bavl}}{{P2}_{gas}} = {\frac{{P2}_{L} + {P2}_{b} - {P2}_{bross}}{{P2}_{g} + {P2}_{gross}} = \frac{{P2}_{g} - {P2}_{bross}}{{P2}_{g} + {P2}_{gross}}}}} & (3)\end{matrix}$

[0098] As described above, characteristics of power loss P2_(bross)against input power P2_(b) of the battery 63 and characteristics ofpower loss P2_(gross) of the engine and the generator against outputpower P2_(g) of the generator 62 are approximated by quadraticexpressions represented with the following expressions (4) and (5)respectively.

P2_(bross) =a×P2_(b) ² +b×P2_(b) +c  (4)

P2_(gross) =α×P2_(g) ² +β×P2_(g)+γ  (5)

[0099] In addition, output power P2_(g) of the generator 62, input powerP2_(b) of the battery 63, and power consumption P2_(L) of the electricactuator 64 satisfy the following relationship represented with theexpression (6).

P2_(b) =P2_(g) −P2_(L)  (6)

[0100] The following expression (7) is obtained by transforming theforegoing expression (3) using the foregoing expression (4), (5), and(6). $\begin{matrix}{\eta = \frac{{{- a} \times \quad {P2}_{g}^{2}} + \quad {\left( {1 - \quad b + \quad {2 \times \quad a \times \quad {P2}_{L}}} \right) \times \quad {P2}_{g}} + \quad {b \times \quad {P2}_{L}} - \quad c - \quad {a \times \quad {P2}_{g}^{2}}}{{\alpha \times {P2}_{g}^{2}} + {\left( {1 + \beta} \right) \times {P2}_{g}} + \gamma}} & (7)\end{matrix}$

[0101] Output power P2_(g) of the generator that maximizes the ηobtained by the foregoing expression (7) is obtained by the followingexpression (8) under conditions P2_(g)≧0 and P2_(b)≧0. $\begin{matrix}{\frac{\eta}{{P2}_{g}} = 0} & (8)\end{matrix}$

[0102] This expression (8) leads to a relationship represented with thefollowing expression (9).

k×P2_(g) ² +l×P2_(g) +m=0  (9)

[0103] where

k=−2×a×α×P2_(L) −a×β+b×α−a−α

l=2×a×α×P2_(L) ²−2×b×α×P2_(L)−2×a×γ+2×c×α

m=c+c×β+γ−b×γ

−b×P2_(L)−b×β×P2_(L)+2×a×γ×P2_(L)+a×P2_(L) ²+a×β×P2_(L) ²

[0104] A solution represented by the following expression (10) isobtained by solving the foregoing expression (9). $\begin{matrix}{{P2}_{g} = \frac{{- 1} + \sqrt{l^{2} - {4 \times k \times m}}}{2 \times k}} & (10)\end{matrix}$

[0105] Further, output power P2_(g) of the generator 62 is calculatedsubstituting the power consumption (required power) P2_(L) of theelectric actuator 64 detected by the load power detecting unit 80 forthe foregoing expression (10). Furthermore, input power P2_(b) of thebattery 62 is calculated substituting the power consumption P2_(L) ofthe electric actuator 64 and the output power P2_(g) for the foregoingexpression (6).

[0106] Efficiency η of the entire system is best improved and fuelconsumption of the engine is also improved by controlling generation andcharge by the generator 62 and the battery 63 respectively to the outputpower P2_(g) of the generator and the input power P2_(b) of the batteryas calculated above.

[0107] In addition, a power controlling method in the power controllingmechanism 9, which has the foregoing configuration, will hereinafter bedescribed referring to FIG. 15. It should be noted that FIG. 15 is aflowchart showing a process of the power controlling method by the powercontrolling mechanism shown in FIG. 10.

[0108] In step S301, the battery state-of-charge detecting unit 74calculates state-of-charge SOC of the battery 63 using the outputcurrent I_(b) of the battery 63 inputted from the battery current sensor72 and the voltage V_(b) between terminals of the battery 63 inputtedfrom the battery voltage sensor 73, with the voltage V_(b) betweenterminals being corrected by the temperature TEMP_(b) of the battery 63inputted from the battery temperature sensor 71, and then outputs thestate-of-charge SOC as a calculation result at the battery power-losscharacteristics determining unit 91.

[0109] In step S302, the battery power-loss characteristics determiningunit 91 determines coefficients (a, b, c) of quadratic expression in anapproximation of loss characteristics of the battery 63 using thetemperature TEMP_(b) of the battery 63 inputted from the batterytemperature sensor 71 and the state-of-charge SOC of the battery 63inputted from the battery state-of-charge detecting unit 74, and thenoutputs the coefficients (a, b, c) as a determination result at thegenerator/battery power distribution determining unit 93.

[0110] In step S303, the generator output power-loss characteristicsdetermining unit 92 determines coefficients (α, β, γ) of quadraticexpression in an approximation of loss characteristics of the engine 61and the generator 62, and then outputs the coefficients (α, β, γ) as adetermination result at the generator/battery power distributiondetermining unit 93.

[0111] In step S304, the load power detecting unit 80 detects requiredpower P2_(L) for the electric actuator 64 based on the load voltageinputted from the load voltage sensor 78 and the load current inputtedfrom the load current sensor 79, and then outputs the required powerP2_(L) at the generator/battery power distribution determining unit 93.

[0112] In step S305, the generator/battery power distributiondetermining unit 93 calculates output power P2_(g) of the generator byoperating the foregoing expression (10) using the required power P2_(L)for the electric actuator 64, the coefficients (a, b, c) inputted fromthe battery power-loss characteristics determining unit 91, and thecoefficients (α, β, γ) inputted from the generator output power-losscharacteristics determining unit 92. Then, the generator/battery powerdistribution determining unit 93 outputs a command signal including thecalculated output power P2_(g) at the generator power controlling unit83. In addition, the generator/battery power distribution determiningunit 93 calculates input power P2_(b) of the battery 63 by operating theforegoing expression (6) using the required power P2_(L) for theelectric actuator 64 and the calculated output power P2_(g) of thegenerator 62, and then outputs another command signal including thecalculated input power P2_(b) at the battery power controlling unit 82.

[0113] In step S306, the battery power controlling unit 82 controlscharge of the battery 63 to the input power P2_(b) indicated by thecommand signal input from the generator/battery power distributiondetermining unit 93. In contrast, the generator power controlling unit83 controls generation of the generator 62 to the input power P2_(g)indicated by the command signal inputted from the generator/batterypower distribution determining unit 93.

[0114] In accordance with the power controlling mechanism 9 for thehybrid excavator 1 according to the second embodiment of the presentinvention, total energy loss of the hybrid construction machine isreduced and then fuel consumption of the engine is improved, wherein theoutput power of the generator 62 and the input power of the battery 61are determined taking into consideration loss characteristics of thegenerator 62 and the engine 61 against output of the generator 62, andloss characteristics of the battery 61 against input power.

[0115] Although preferred embodiments for the present invention aredescribed above, the invention is not restrictive to the presentembodiments and various design changes may come within the meaning andrange of equivalency of the claims.

INDUSTRIAL APPLICABILITY

[0116] The power controller described above is applicable to a hybridconstruction machine such as a hybrid excavator and the like including agenerator and an electrical energy storage unit.

1. A power controller for hybrid construction machine including an engine, a generator which is driven by said engine, an electrical energy storage unit to store electric power generated by said generator, and one or more electric actuators driven by said generator and said electrical energy storage unit, characterized by comprising: a load power detecting means to detect required power for said one or more electric actuators; a charging power setting means to set maximum value of charging power of said electrical energy storage unit; a discharging power setting means to set maximum value of discharging power of said electrical energy storage unit; a generator output power setting means to set upper limit and lower limit value of output power of said generator; a power distribution determining means to determine power distribution between said generator and said electrical energy storage unit based on the set value by said charging power setting means, the set value by said discharging power setting means, the set value by said generator output power setting means, and the detection result by said load power detecting means; a generator power controlling means to control the output power of said generator based on the determination result by said power distribution determining means; and a power controlling means for electrical energy storage unit to control charging/discharging power of said electrical energy storage unit based on the determination result by said power distribution determining means.
 2. The power controller for hybrid construction machine according to claim 1, characterized by further comprising a state-of-charge detecting means to detect state-of-charge of said electrical energy storage unit, wherein said generator output power setting means sets upper limit and lower limit value of the output power of said generator based on the detection result by said state-of-charge detecting means.
 3. The power controller for hybrid construction machine according to claim 1, characterized by further comprising a state-of-charge detecting means to detect state-of-charge of said electrical energy storage unit, wherein said charging power setting means sets maximum value of the charging power of said electrical energy storage unit based on the detection result by said state-of-charge detecting means, and said discharging power setting means sets maximum value of the discharging power of said electrical energy storage unit based on the detection result by said state-of-charge detecting means.
 4. The power controller for hybrid construction machine according to claim 1, characterized by further comprising a temperature detecting means to detect temperature of said electrical energy storage unit, wherein said charging power setting means sets maximum value of the charging power of said electrical energy storage unit based on the detection result by said temperature detecting means, and said discharging power setting means sets maximum value of the discharging power of said electrical energy storage unit based on the detection result by said temperature detecting means.
 5. A power controller for hybrid construction machine including an engine, a generator which is driven by said engine, an electrical energy storage unit to store electric power generated by said generator, and one or more electric actuators driven by said generator and said electrical energy storage unit, characterized by comprising: a load power detecting means to detect required power for said one or more electric actuators; a power distribution determining means to determine power distribution between said generator and said electrical energy storage unit to maximize power consumption efficiency by said engine, utilizing the required power detected by said load power detecting means, loss characteristics of said generator and said engine against an output power of said generator, and loss characteristics of said electrical energy storage unit against an input power of said electrical energy storage unit; a generator power controlling means to control the output power of said generator based on the determination result by said power distribution determining means; and a power controlling means for electrical energy storage unit to control the input power of said electrical energy storage unit based on the determination result by said power distribution determining means.
 6. The power controller for hybrid construction machine according to claim 5, characterized by further comprising: a temperature detecting means to detect temperature of said electrical energy storage unit; and a power loss characteristics determining means for electrical energy storage unit to determine the loss characteristics of said electrical energy storage unit against the input power of said electrical energy storage unit based on the detection result by said temperature detecting unit.
 7. The power controller for hybrid construction machine according to claim 5, characterized by further comprising: a state-of-charge detecting means to detect state-of-charge of said electrical energy storage unit; and a power loss characteristics determining means for electrical energy storage unit to determine the loss characteristics of said electrical energy storage unit against the input power of said electrical energy storage unit based on the detection result by said state-of-charge detecting unit. 